import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

/**
 * This class, designed to be used in conjunction with Paint, makes it possible
 * to create animated drawings.
 *
 */

public class PaintAnimator extends TimerTask {

  /**
   * The objects to be animated at each time step.
   */

  private List<Object> toanimate_ = new ArrayList<Object>();

  /**
   * The timer that invokes the animation.
   */

  private Timer timer_;

  /**
   * Create a new animator which will perform one animation step every 'delay'
   * milliseconds.
   *
   * @param delay
   *          number of ms between animation steps
   */

  public PaintAnimator ( long delay ) {
    timer_ = new Timer();
    timer_.schedule(this,delay,delay);
  }

  /**
   * Start animating an object. The object must have a method of the form
   *
   * <pre>
   *   public void doAnimateStep () { ... }
   * </pre>
   *
   * doAnimateStep will be called for each step of the animation, and should
   * handle updating whatever needs to be updated (e.g. changing the position)
   * and drawing the new thing.
   *
   * @param obj
   *          object to animate
   */

  public void animate ( Object obj ) {
    toanimate_.add(obj);
  }

  /**
   * Stop animating an object. doAnimateStep() will no longer be called for the
   * specified object.
   *
   * @param obj
   *          object to stop animating
   */

  public void unanimate ( Object obj ) {
    toanimate_.remove(obj);
  }

  /**
   * Carry out one animation step for each thing being animated. This method is
   * used by the Java system, and should not be called directly.
   */
  @Override
  public void run () {
    // clear the window
    Paint.clear();

    // animate the objects
    for ( Object obj : toanimate_ ) {
      try {
	Method method =
	  obj.getClass().getMethod("doAnimateStep",(Class[]) null);
	method.invoke(obj,(Object[]) null);

      } catch ( SecurityException e ) {
	System.out.println("something went wrong with animating object " + obj);
	e.printStackTrace();
      } catch ( NoSuchMethodException e ) {
	System.out.println("cannot animate object " + obj + " because it "+
			   "does not have a doAnimateStep() method");
	e.printStackTrace();
      } catch ( IllegalArgumentException e ) {
	System.out.println("something went wrong with animating object " + obj);
	e.printStackTrace();
      } catch ( IllegalAccessException e ) {
	System.out.println("something went wrong with animating object " + obj);
	e.printStackTrace();
      } catch ( InvocationTargetException e ) {
	System.out.println("something went wrong with animating object " + obj);
	e.printStackTrace();
      }

    }
  }

}